A toothbrush is composed of a brush projecting from one side of the end of a handle. Electric toothbrushes, in which the toothbrush is electrically driven, are available in a bus-brushing type where the toothbrush moves in a reciprocating rectilinear fashion in the direction of the axis of its handle, and in a rolling-brushing type where the toothbrush moves in a reciprocating fashion about the axis of its handle.
With the bus-brushing type, however, the brush of the toothbrush can get trapped between teeth, particularly between molars, so that the stroke becomes small and reduces scrubbing effectiveness. With the rolling-brushing type, there is a risk of gums being folded back or of injury being inflicted to the gums.
Another electric toothbrush is available in which a brush is mounted on a rotating base and moves in a reciprocating fashion about an axis in the direction of brush projection, but since this device requires that the brush be placed against each individual tooth, brushing of teeth takes an extremely long time.